1. Field of the Invention
The present invention relates to a composite push rod that is provided with two specially shaped ends to which metal end fittings bond via mating surfaces provided on the metal end fittings. The unique shape of the ends of the composite push bar and the mating surfaces on the metal end fittings evenly distribute stress that is exerted on the metal end fittings to the composite push bar. The push bar is constructed of a plurality of layers of sheets of epoxy impregnated, longitudinally oriented fiber material that form the inner portion of the push bar and a single outside sheet of epoxy impregnated, woven fiber material that forms the outside portion of the push bar. The layers of fiber material are thermo-set to form the composite bar. The ends of the composite bar are then cut to the proper shape and the metal end fittings are bonded to the ends of the composite bar via epoxy.
2. Description of the Related Art
Composite push rods are known as lighter weight replacements for metallic push rods in use between a cam shaft and a valve rocker in internal combustion engines for the purpose of reducing the weight of the push rod and thereby increasing the fuel economy and power of the engine or automobile in which the engine is used. These composite push rods are constructed of a bar that is made of composite material, such as carbon fiber. These composite push, bars generally have flat ends to which rounded metal end fittings are bonded, usually by some type of epoxy or adhesive. The composite push rod then attaches to the cam shaft and valve rocker via these rounded metal end fittings. A more complete description of one such composite push rod is contained in U.S. Pat. No. 4,186,696 which issued on Feb. 5, 1980 to Don R. Linsenmann.
One of the problems with these composite push rods is that the mechanical stress exerted on the push bars when they are under load conditions causes the composite bar to fray or broom where it attaches to the rounded metal end fittings, thereby weakening the bar at its ends and shortening the life of the composite push rod.
The present invention addresses this problem by employing a unique two-angled end on the composite bar to which mating surfaces are provided on each of the metal end fittings. This unique two-angled junction between the metal end fittings and the composite bar allows the stress to be transferred between the metal end fittings and the bar more evenly and efficiently, thereby preventing fraying of the bar at its ends. Also, the present invention is created from a stronger bar than taught in prior art patents because it employs more layers or sheets of longitudinally oriented fiber material in the construction on the bar's inner core.